link to documentation

[ms502040]

make link to documentation in package manifest:

"documentationUrl": "https://github.com/rfadeev/pump-editor/wiki"

[rfadeev]

Hi,

Thank you for the contribution! I have added the link, please update to version 1.0.5. Clicking the "View documentation" from Package Manager window should open the link for Unity 2020.1.0 and newer.